Pump



Sept. 29., 1936.

R. J. S. PIGOTT PUMP Filed Oct. 11, 1935 3 Sheets-Sheet l WW QN QM W ayx M Gnom u Sept. 29, 1936 J 5 PIGQTT 7 2,055,587

PUMP

Filed Oct. 11, 1955 5 Sheets-Sheet 2 gwu cwim Sept. 29, 1936. 5 PIGQTT2,055,587

PUMP

Filed Oct. 11, 1935 3 Sheets-Sheet 3 F- J5. P gyo t MSW/W Patented Sept.29, 1936 UNITED STATES PATENT OFFICE PUMP Reginald J. S. Pigott,Pittsburgh, Pa., assignor to Gulf Research & Development Company,Pittsburgh, Pa., a corporation of Delaware Application October 11, 1935,Serial No. 44 ,626 1 Claim. (Cl. 103-5) This invention relates to pumps;and it comenough to reduce the pressure on the liquid beprises incombination with a pump of the rotary low saturation point orvaporizationpoint, and positive displacement type adapted to pump liqgasis suddenly evolved from the liquid in the uids and having twointerengaging main pressure suction side of the pump. The amount of gas5 pump members, one of which rotates at higher evolved is considerablein many cases. In one 5 speed than the other, means for raising theprestest on pumping a crude petroleum, the volume of sure of liquid justbefore delivery into the inlet gas evolved in a certain pump of the typedeside of the main pressure pumping members in orscribed was 25 per centof the volumetric capacity der to prevent formation of vapor in thepump, of the pump.

said means comprising a rotary impeller of a The presence of gas in thepump while pumping 10 type adapted to develop pressure by rotationalliquids is deleterious. The gas reduces the voluvelocity, the impellerbeing operatively connected metric capacity and the efliciency of thepump with, and driven by, the main pumping member since the pump isunder the necessity of acting as which runs at the higher speed, theimpeller being a compressor as well as a pump. A further disof largerdiameter than either of the two main advantage is that the gas bubblesas they pass 15 pumping members, andacasing enclosing the imfrom suctionto discharge pressure in the pump peller and having an inlet connectionfor liquid are abruptly compressed and collapsed, thereby to be pumpeddelivering to the impeller and also causing considerable vibration inthe oil column a liquid connection from the impeller to the inlet on thedischarge side of the pump. This effect side of the main pumpingmembers; the impeller may give rise to destructive vibration in the 20and casing therefor in some modifications being pressure piping and isattended by noise and adapted for ready attachment to and detachmentrattle in the pump. The gas evolvingefiect defrom the main pressure pumpproper and for rescribed is inherent in the operation of rotaryplacement with a plain head; all as more fully positive displacementpumps and is aggravated hereinafter set forth and as claimed. at highrotational speeds. It may even occur in 25 There has recently beendeveloped an improved the case of reciprocating pumps when these aretype of rotary pump having a rotating ring gear operated at a highpiston speed. and a pinion engaging the ring gear and having Oneachieved object of the invention is the proone less tooth than the ringgear; the tooth shape vision of a ring gear and pinion type pump inbeing such that during rotation of the two gears which gas formation inthe pump is prevented. I 30 a plurality of expanding and contractingchamdo this by providing means for imposing a small bers are formed ininter-tooth spaces. The two plus pressure on the liquid entering thepump; gears are mounted for rotation in a casing which a pressureslightly more than sufficient to overhas abutments separating the sideof the gear come pressure drop in the pump due to acceleracombinationwherein the inter-tooth chambers tion. There is provided in combinationwith the 35 are constantly expanding (inlet side) from the pump, animpeller, of the type adapted to develop opposite side, in which thechambers are cona pressure by rotational velocity (the so-called stantlycontracting (outlet side). These pumps centrifugal or propeller type),which is larger in are highly eiiicient mechanically andvolumetridiameter than the ring and which is rotated di- 4 cally. Theyare of the true/positive displacement rectly by the pinion; that is, themember which type and are able to deliver at pressures of sevruns athigher speed. The diameter of the imeral hundred pounds Wr q inch- ThePumps peller is proportioned so as to be enough larger are ad p d 19011111 at g Speed; Speeds around than that of the ring gear as tocompensate for 1200 The pmlfm for example may be the total pressure dropincluding that due to aca ggggi gg ifg g ggf g the ring gear celerationand that due to frictional losses beruns at a rather high rate. Liquidentering the Egg the Impeller and the inlet of the main um at acomparatively slow rate is accelerated f inlet side of the pump, to theperipheral In theaccompanymg drawings are shown more or lessdiagrammatically, two examples of a spe- 50 s ed of the ring gear. Theacceleration is neces s arily accompanied by a drop in pressure. Incific embodiment of the invention. In the showpumping non-volatileliquids, this makes no difings,

ference. But in pumping liquid saturated t Fig. 1 is a view in centralvertical section of a gas, or liquids almost at their vaporizationpoint, s pu p p ov with an te chan eable the drop in pressure in theinlet is sometimes booster head; 55

Fig. 2 is a sectional view taken along line 2-2 ofFig. 1;

Fig. 3 is an Fig. 1:

Fig. 4 is a view partly in elevation and partly in vertical section ofthe pump of Fig. 1 with the booster head replaced by a plain head;

Fig. 5 is a view in vertical section of one end of a pump provided witha modified booster combination; and 1 Fig. 6 is a view of the boosterimpeller of the pump of Fig. 5.

Referring to the figures, in which like reference characters indicatelike parts, the pump is shown as comprising a'main casing ill of generalhorizontal cylindrical form having a substantially cylindrical cavity 9therein, a vertically extending outlet i I with fluid conduit l2 thereinand a flange l3 for attachment to pipe etc. Casing l0 has an inlet Hwith a similar flange i5, disposed end elevation corresponding toapproximately at right angles to the outlet. The

casing rests on a rectangular base l8. The pumping members are centrallylocated in the casing. The ring gear comprises a cylindrical gear memberll provided with teeth l8 and annular collars l9 at each end. Mountingsleeves 20 are prorotary races engaging turned portion 28 and the vflxed races being retained in annular recesses 30 in the casing. Thering gear is thus retained for free rotation in the casing. The spacesbetween the ring gear teeth are left open to serve as fluid outlets asindicated at 3|, these spaces being in communication with inlet [4 andoutlet l2. The casing is provided with a suitable upper abutment 35 andlower abutment 36, engaging the periphery of the ring gear andseparating the inlet from the outlet side of the pump.

A pinion 32 is provided engaging the teeth of the ring gear and havingone less tooth than the ring gear; The pinion is keyed to a drive shaft33 by a key indicated at 34. The axis of the drive shaft is eccentricwith respect to the axis of the ring gear and of the casing. The driveshaft is rotatably. mounted by means of two bearings, shown as rollerbearings 48 having sleeves 4| tightly fitted to the drive shaft. At theright end of the pump (Figs. 1 and 4) a head 42 is provided, of roughlyconical form and bolted in fluid tight connection to casing ill by meansof bolts 43. The head has a bore 44 surrounding shaft 33, containingpacking 45 and stufling nut 46 to prevent leakage around the shaft. Alocking ring or washer 49 for bearing 40 and lock nut 59 threaded onshaft 33 as at 48 are provided as shown.

At the left hand end of the pump is provided the booster combination. Anirregular head 55 having an annular flange 56 is bolted to casing in influid tight connection by means of bolts 43. Head 55 has a cylindricalbore 51 concentric with the axis of the pinion and drive shaft andcontaining second bearing 40 mounted on shaft 33 by sleeve 4i infrictional fltwith the shaft. Thus the pinion and shaft are firmlymounted for rotation at two spaced points. A ring 58 is provided betweenflange 56 and easing ill, to retain bearings 40 and 21 in place. A thinsleeve 59 spaces left hand sleeve 4| from the pinion.

The end head 55 has attached thereto a housing of irregular shape 68with a circular flange 8| provided with holes 82, for attachment of pipeetc., a-volute chamber housing portion 83 and a circular flange 84merged with the volute,

as shown. Housing 60 is attached to head 55 at flange 64, by studs andnuts 54. Housing 88 has a divergent conical inlet 65, coaxial with thepinion and drive shaft and delivering into the volute chamber 66enclosed by portion 63. Member 55 has a frustoconical projection 61 witha bore 68 closely but freely fitting a threaded extension shaft 69firmly attached to shaft 33 by a threaded connection as at 10. The outerend of extension 69 has a shank of reduced diameter 15 and a tip 16,threaded as shown. Mounted on shank 15 is an impeller ll, keyed theretoas at 18 and retained by a rounded cap nut 19 threaded on tip 18. Theimpeller has a plurality of angularly disposed blades 80. The cap 19,the interblade portion of the impeller and projection 6! merge into asmooth and rounded shape as is apparent in Fig. l. The blades of theimpeller extend towards chamber 66 leaving a slight clearance 85adjacent the junction of inlet 65 with chamber 66. The diameter of theimpeller is greater than the diameter of the ring gear.

Volute chamber 66 has an outlet 86 with outlet passage 81. Outlet 86 hasa flange 88. A double bent conduit 89 having flanges 98 at each end isbolted as at I to outlet 86 and to the flange l5 of the pump inlet. Thusthe impeller draws from inlet 65 and delivers through outlet 86, conduit89 and inlet i4 to the main pump.

In operation, the pump is driven through drive shaft 33 by an electricmotor or other power means (not shown) at a fairly high speed. Inlet 65being in communication with liquid, impeller Tl draws liquid intovolutechamber 66 and delivers liquid under slight pressure to the inletof the pump proper. The rapidly rotating ring gear and pinioncombination ll, 32 tends to reduce pressure at the pump inlet; but sincethe liquid is under suficient positive pressure, there is no net drop.Liquid is delivered through outlet i2.

When gassy liquids are pumped, liquids are kept under pressure from themoment they reach inlet 65 and there is no chance for evolution of gas.The pump runs quietly and smoothly at high eiiiciency.

The diameter of the impeller is made a little l 'arger than that merelynecessary to compensate for pressure drop due to acceleration, so as toalso compensate for frictional losses in the fluid conduits 81, 89 andI4 and still provide a slight plus pressure in the main pump inlet.

The booster-head shown is readily interchangeablewith an ordinary headin case it is desired to dispense with the booster. Referring to Fig. 4.a simple cap-like head I00 is provided, having a flange lili similar toflange 56 on the booster head and retained to the casing by bolts 43.The head has a bore I51 of the same size as the bore 51 in the boosterhead,'and bearing 40 is retained therein, a retaining shoulder I02 beingprovided. Threaded bore I0 is advantageously utilized in thismodification, to supplement friction in retaining the shaft in thebearing sleeve 4i. As shown, a retaining bolt 99 is provided, engagingthe threads in the shaft end and engaging a retaining ring 9, similar toring 49 shown at the right hand end of Fig. 1. However, the bolt andring can often be omitted; frictional contact between the bearing sleeveand the shaft being suflicient.

In replacing the booster head with the plain head, it is merelynecessary to take of! the booster head containing its bearing 40 andunscrew extension 69, and then slip on plain head it with its bearing40. Sometimes, instead of providing the threaded extension 69, it ismore convenient to make shaft portion 69 and 33 in one piece, the entireshaft in this case being taken out and replaced with a shorter one whenthe change is made.

In the embodiment of the invention described, the booster impeller isof. the propeller type. Sometimes it is more convenient to employ acentrifugal type booster impeller. Figs. 5 and 6 illustrate such amodification. The booster casing is made in two pieces: a bearinghousing and a centrifugal volute housing III attached thereto. Thevolute housing has an inlet portion H2 flanged as at 6|, and avolutechamber H3 of the typical shape for centrifugal devices. Shank 69 ofunitary shaft I09 is mounted in housing 0 by bearing 40. Extension 15 isprovided with a centrifugal impeller, comprising a discoid hub H4 andradial blades H5. retained on the shaft by a nut H6 and a key H8. Aspacing disk I" separates the impeller from bearing 40. The out let 81of volute chamber H is in communication with the inlet of the pump asdescribed in connection with the propeller modification. The

diameter of the centrifugal impeller is considerably greater than thatof the ring gear.

In operation, the centrifugal impeller boosts the pressure, to producethe same eifect as described in the case of the propeller modification.

What I claim is:

A pump of the rotary positive displacement type having a chamberedcasing provided with an inlet and an outlet, a pinion and ring gearserving as pumping members, the pinion rotating at higher speed than thering gear, means for rotatably mounting the ring gear in the casing, ashaft secured to the pinion, a head at each end of the casing, bearingmeans in each of said heads for the shaft, an impeller of. a typeadapted to develop pressure by rotational velocity in one of the heads,a detachable shaft extension on the end of the shaft extending into saidhead, the impeller being secured to the shaft extension, an impellerhousing surrounding the impeller and having an inlet connectiondelivering liquid to the impeller and having also a detachable outletconnection from the impeller to the inlet side of the gears, and meansfor detachably securing the impeller housing and head to the casing, sothat the head, bearing therein, housing, impeller and shaft extensioncan be removed from the casing.

REGINALD J. S. PIGOTT.

